File system for a capture system

ABSTRACT

A file system can be provided in a capture system to efficiently read and write captured objects. In one embodiment, such a file system includes a plurality of queues to queue captured objects to be written to a disk, each queue being associated with one of a plurality of object types, and each queue containing captured objects of the type associated with each queue. A scheduler can be provided to select one of the plurality of queues, and a block manager to select a partition of a disk, the partition being associated with the object type of the captured objects in the selected queue. A disk controller configured to write contiguous blocks of data from the selected queue to the selected partition is connected to the block manager to enable writing to a disk.

PRIORITY AND RELATED APPLICATIONS

This patent application is a continuation of (and claims the benefit ofpriority under 35 U.S.C. §120) of U.S. application Ser. No. 11/168,104,filed Jun. 27, 2005 now U.S. Pat. No. 7,949,849, entitled “File Systemfor a Capture System”, Inventor(s) Rick Lowe. The disclosure of theprior application is considered part of (and is incorporated byreference in) the disclosure of this application. This applicationfurther claims the priority benefit of U.S. Provisional Application60/604,197, entitled “File System for a Capture System,” filed on Aug.24, 2004 and U.S. Provisional Application 60/604,311, entitled “FileSystem Scheduler for a Capture System,” filed on Aug. 24, 2004. Thedisclosure of the prior applications is considered part of (and isincorporated by reference in) the disclosure of this application.

FIELD OF THE INVENTION

The present invention relates to computer networks, and in particular,to a file system.

BACKGROUND

Computer networks and systems have become indispensable tools for modernbusiness. Modern enterprises use such networks for communications andfor storage. The information and data stored on the network of abusiness enterprise is often a highly valuable asset. Modern enterprisesuse numerous tools to keep outsiders, intruders, and unauthorizedpersonnel from accessing valuable information stored on the network.These tools include firewalls, intrusion detection systems, and packetsniffer devices. However, once an intruder has gained access tosensitive content, there is no network device that can prevent theelectronic transmission of the content from the network to outside thenetwork. Similarly, there is no network device that can analyse the dataleaving the network to monitor for policy violations, and make itpossible to track down information leeks. What is needed is acomprehensive system to capture, store, and analyse all datacommunicated using the enterprises network.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereference numerals refer to similar elements and in which:

FIG. 1 is a block diagram illustrating a computer network connected tothe Internet;

FIG. 2 is a block diagram illustrating one configuration of a capturesystem according to one embodiment of the present invention;

FIG. 3 is a block diagram illustrating the capture system according toone embodiment of the present invention;

FIG. 4 is a block diagram illustrating an object assembly moduleaccording to one embodiment of the present invention;

FIG. 5 is a block diagram illustrating an object store module accordingto one embodiment of the present invention;

FIG. 6 is a block diagram illustrating an example hardware architecturefor a capture system according to one embodiment of the presentinvention;

FIG. 7 is a block diagram illustrating a file system for a capturedevice according to one embodiment of the present invention;

FIG. 8 is a block diagram illustrating a more detailed version of thefile system of FIG. 7, according to one embodiment of the presentinvention; and

FIG. 9 is a flow diagram illustrating object read and write operations,according to one embodiment of the present invention.

DETAILED DESCRIPTION

Although the present system will be discussed with reference to variousillustrated examples, these examples should not be read to limit thebroader spirit and scope of the present invention. Some portions of thedetailed description that follows are presented in terms of algorithmsand symbolic representations of operations on data within a computermemory. These algorithmic descriptions and representations are the meansused by those skilled in the computer science arts to most effectivelyconvey the substance of their work to others skilled in the art. Analgorithm is here, and generally, conceived to be a self-consistentsequence of steps leading to a desired result. The steps are thoserequiring physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared and otherwise manipulated.

It has proven convenient at times, principally for reasons of commonusage, to refer to these signals as bits, values, elements, symbols,characters, terms, numbers or the like. It should be borne in mind,however, that all of these and similar terms are to be associated withthe appropriate physical quantities and are merely convenient labelsapplied to these quantities. Unless specifically stated otherwise, itwill be appreciated that throughout the description of the presentinvention, use of terms such as “processing”, “computing”,“calculating”, “determining”, “displaying” or the like, refer to theaction and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

As indicated above, one embodiment of the present invention isinstantiated in computer software, that is, computer readableinstructions, which, when executed by one or more computerprocessors/systems, instruct the processors/systems to perform thedesignated actions. Such computer software may be resident in one ormore computer readable media, such as hard drives, CD-ROMs, DVD-ROMs,read-only memory, read-write memory and so on. Such software may bedistributed on one or more of these media, or may be made available fordownload across one or more computer networks (e.g., the Internet).Regardless of the format, the computer programming, rendering andprocessing techniques discussed herein are simply examples of the typesof programming, rendering and processing techniques that may be used toimplement aspects of the present invention. These examples should in noway limit the present invention, which is best understood with referenceto the claims that follow this description.

Networks

FIG. 1 illustrates a simple prior art configuration of a local areanetwork (LAN) 10 connected to the Internet 12. Connected to the LAN 102are various components, such as servers 14, clients 16, and switch 18.There are numerous other known networking components and computingdevices that can be connected to the LAN 10. The LAN 10 can beimplemented using various wireline or wireless technologies, such asEthernet and 802.11b. The LAN 10 may be much more complex than thesimplified diagram in FIG. 1, and may be connected to other LANs aswell.

In FIG. 1, the LAN 10 is connected to the Internet 12 via a router 20.This router 20 can be used to implement a firewall, which are widelyused to give users of the LAN 10 secure access to the Internet 12 aswell as to separate a company's public Web server (can be one of theservers 14) from its internal network, i.e., LAN 10. In one embodiment,any data leaving the LAN 10 towards the Internet 12 must pass throughthe router 12. However, there the router 20 merely forwards packets tothe Internet 12. The router 20 cannot capture, analyze, and searchablystore the content contained in the forwarded packets.

One embodiment of the present invention is now illustrated withreference to FIG. 2. FIG. 2 shows the same simplified configuration ofconnecting the LAN 10 to the Internet 12 via the router 20. However, inFIG. 2, the router 20 is also connected to a capture system 22. In oneembodiment, the router 12 splits the outgoing data stream, and forwardsone copy to the Internet 12 and the other copy to the capture system 22.

There are various other possible configurations. For example, the router12 can also forward a copy of all incoming data to the capture system 22as well. Furthermore, the capture system 22 can be configuredsequentially in front of, or behind the router 20, however this makesthe capture system 22 a critical component in connecting to the Internet12. In systems where a router 12 is not used at all, the capture systemcan be interposed directly between the LAN 10 and the Internet 12. Inone embodiment, the capture system 22 has a user interface accessiblefrom a LAN-attached device, such as a client 16.

In one embodiment, the capture system 22 intercepts all data leaving thenetwork. In other embodiments, the capture system can also intercept alldata being communicated inside the network 10. In one embodiment, thecapture system 22 reconstructs the documents leaving the network 10, andstores them in a searchable fashion. The capture system 22 can then beused to search and sort through all documents that have left the network10. There are many reasons such documents may be of interest, includingnetwork security reasons, intellectual property concerns, corporategovernance regulations, and other corporate policy concerns.

Capture System

One embodiment of the present invention is now described with referenceto FIG. 3. FIG. 3 shows one embodiment of the capture system 22 in moredetail. The capture system 22 includes a network interface module 24 toreceive the data from the network 10 or the router 20. In oneembodiment, the network interface module 24 is implemented using one ormore network interface cards (NIC), e.g., Ethernet cards. In oneembodiment, the router 20 delivers all data leaving the network to thenetwork interface module 24.

The captured raw data is then passed to a packet capture module 26. Inone embodiment, the packet capture module 26 extracts data packets fromthe data stream received from the network interface module 24. In oneembodiment, the packet capture module 26 reconstructs Ethernet packetsfrom multiple sources to multiple destinations for the raw data stream.

In one embodiment, the packets are then provided the object assemblymodule 28. The object assembly module 28 reconstructs the objects beingtransmitted by the packets. For example, when a document is transmitted,e.g. as an email attachment, it is broken down into packets according tovarious data transfer protocols such as Transmission ControlProtocol/Internet Protocol (TCP/IP) and Ethernet. The object assemblymodule 28 can reconstruct the document from the captured packets.

One embodiment of the object assembly module 28 is now described in moredetail with reference to FIG. 4. When packets first enter the objectassembly module, they are first provided to a reassembler 36. In oneembodiment, the reassembler 36 groups—assembles—the packets into uniqueflows. For example, a flow can be defined as packets with identicalSource IP and Destination IP addresses as well as identical TCP Sourceand Destination Ports. That is, the reassembler 36 can organize a packetstream by sender and recipient.

In one embodiment, the reassembler 36 begins a new flow upon theobservation of a starting packet defined by the data transfer protocol.For a TCP/IP embodiment, the starting packet is generally referred to asthe “SYN” packet. The flow can terminate upon observation of a finishingpacket, e.g., a “Reset” or “FIN” packet in TCP/IP. If now finishingpacket is observed by the reassembler 36 within some time constraint, itcan terminate the flow via a timeout mechanism. In an embodiment usingthe TPC protocol, a TCP flow contains an ordered sequence of packetsthat can be assembled into a contiguous data stream by the ressembler36. Thus, in one embodiment, a flow is an ordered data stream of asingle communication between a source and a destination.

The flown assembled by the reassember 36 can then is provided to aprotocol demultiplexer (demux) 38. In one embodiment, the protocol demux38 sorts assembled flows using the TCP Ports. This can includeperforming a speculative classification of the flow contents based onthe association of well-known port numbers with specified protocols. Forexample, Web Hyper Text Transfer Protocol (HTTP) packets—i.e., Webtraffic—are typically associated with port 80, File Transfer Protocol(FTP) packets with port 20, Kerberos authentication packets with port88, and so on. Thus in one embodiment, the protocol demux 38 separatesall the different protocols in one flow.

In one embodiment, a protocol classifier 40 also sorts the flows inaddition to the protocol demux 38. In one embodiment, the protocolclassifier 40—operating either in parallel or in sequence with theprotocol demux 38—applies signature filters to the flows to attempt toidentify the protocol based solely on the transported data. Furthermore,the protocol demux 38 can make a classification decision based on portnumber, which is subsequently overridden by protocol classifier 40. Forexample, if an individual or program attempted to masquerade an illicitcommunication (such as file sharing) using an apparently benign portsuch as port 80 (commonly used for HTTP Web browsing), the protocolclassifier 40 would use protocol signatures, i.e., the characteristicdata sequences of defined protocols, to verify the speculativeclassification performed by protocol demux 38.

In one embodiment, the object assembly module 28 outputs each floworganized by protocol, which represent the underlying objects. Referringagain to FIG. 3, these objects can then be handed over to the objectclassification module 30 (sometimes also referred to as the “contentclassifier”) for classification based on content. A classified flow maystill contain multiple content objects depending on the protocol used.For example, protocols such as HTTP (Internet Web Surfing) may containover 100 objects of any number of content types in a single flow. Todeconstruct the flow, each object contained in the flow is individuallyextracted, and decoded, if necessary, by the object classificationmodule 30.

The object classification module 30 uses the inherent properties andsignatures of various documents to determine the content type of eachobject. For example, a Word document has a signature that is distinctfrom a PowerPoint document, or an Email document. The objectclassification module 30 can extract out each individual object and sortthem out by such content types. Such classification renders the presentinvention immune from cases where a malicious user has altered a fileextension or other property in an attempt to avoid detection of illicitactivity.

In one embodiment, the object classification module 30 determineswhether each object should be stored or discarded. In one embodiment,this determination is based on a various capture rules. For example, acapture rule can indicate that Web Traffic should be discarded. Anothercapture rule can indicate that all PowerPoint documents should bestored, except for ones originating from the CEO's IP address. Suchcapture rules can be implemented as regular expressions, or by othersimilar means. Several embodiments of the object classification module30 are described in more detail further below.

In one embodiment, the capture rules are authored by users of thecapture system 22. The capture system 22 is made accessible to anynetwork-connected machine through the network interface module 24 anduser interface 34. In one embodiment, the user interface 34 is agraphical user interface providing the user with friendly access to thevarious features of the capture system 22. For example, the userinterface 34 can provide a capture rule authoring tool that allows usersto write and implement any capture rule desired, which are then appliedby the object classification module 30 when determining whether eachobject should be stored. The user interface 34 can alsoprovide-pre-configured capture rules that the user can select from alongwith an explanation of the operation of such standard included capturerules. In one embodiment, the default capture rule implemented by theobject classification module 30 captures all objects leaving the network10.

If the capture of an object is mandated by the capture rules, the objectclassification module 30 can also determine where in the object storemodule 32 the captured object should be stored. With reference to FIG.5, in one embodiment, the objects are stored in a content store 44memory block. Within the content store 44 are files 46 divided up bycontent type. Thus, for example, if the object classification moduledetermines that an object is a Word document that should be stored, itcan store it in the file 46 reserved for Word documents. In oneembodiment, the object store module 32 is integrally included in thecapture system 22. In other embodiments, the object store module can beexternal—entirely or in part—using, for example, some network storagetechnique such as network attached storage (NAS) and storage areanetwork (SAN).

Tag Data Structure

In one embodiment, the content store is a canonical storage location,simply a place to deposit the captured objects. The indexing of theobjects stored in the content store 44 is accomplished using a tagdatabase 42. In one embodiment, the tag database 42 is a database datastructure in which each record is a “tag” that indexes an object in thecontent store 44 and contains relevant information about the storedobject. An example of a tag record in the tag database 42 that indexesan object stored in the content store 44 is set forth in Table 1:

TABLE 1 Field Name Definition MAC Address Ethernet controller MACaddress unique to each capture system Source IP Source Ethernet IPAddress of object Destination IP Destination Ethernet IP Address ofobject Source Port Source TCP/IP Port number of object Destination PortDestination TCP/IP Port number of the object Protocol IP Protocol thatcarried the object Instance Canonical count identifying object within aprotocol capable of carrying multiple data within a single TCP/IPconnection Content Content type of the object Encoding Encoding used bythe protocol carrying object Size Size of object Timestamp Time that theobject was captured Owner User requesting the capture of object (ruleauthor) Configuration Capture rule directing the capture of objectSignature Hash signature of object Tag Signature Hash signature of allpreceding tag fields

There are various other possible tag fields, and some embodiments canomit numerous tag fields listed in Table 1. In other embodiments, thetag database 42 need not be implemented as a database, and a tag neednot be a record. Any data structure capable of indexing an object bystoring relational data over the object can be used as a tag datastructure. Furthermore, the word “tag” is merely descriptive, othernames such as “index” or “relational data store,” would be equallydescriptive, as would any other designation performing similarfunctionality.

The mapping of tags to objects can, in one embodiment, be obtained byusing unique combinations of tag fields to construct an object's name.For example, one such possible combination is an ordered list of theSource IP, Destination IP, Source Port, Destination Port, Instance andTimestamp. Many other such combinations including both shorter andlonger names are possible. In another embodiment, the tag can contain apointer to the storage location where the indexed object is stored.

The tag fields shown in Table 1 can be expressed more generally, toemphasize the underlying information indicated by the tag fields invarious embodiments. Some of these possible generic tag fields are setforth in Table 2:

TABLE 2 Field Name Definition Device Identity Identifier of capturedevice Source Address Origination Address of object Destination AddressDestination Address of object Source Port Origination Port of objectDestination Port Destination Port of the object Protocol Protocol thatcarried the object Instance Canonical count identifying object within aprotocol capable of carrying multiple data within a single connectionContent Content type of the object Encoding Encoding used by theprotocol carrying object Size Size of object Timestamp Time that theobject was captured Owner User requesting the capture of object (ruleauthor) Configuration Capture rule directing the capture of objectSignature Signature of object Tag Signature Signature of all precedingtag fields

For many of the above tag fields in Tables 1 and 2, the definitionadequately describes the relational data contained by each field. Forthe content field, the types of content that the object can be labeledas are numerous. Some example choices for content types (as determined,in one embodiment, by the object classification module 30) are JPEG,GIF, BMP, TIFF, PNG (for objects containing images in these variousformats); Skintone (for objects containing images exposing human skin);PDF, MSWord, Excel, PowerPoint, MSOffice (for objects in these popularapplication formats); HTML, WebMail, SMTP, FTP (for objects captured inthese transmission formats); Telnet, Rlogin, Chat (for communicationconducted using these methods); GZIP, ZIP, TAR (for archives orcollections of other objects); Basic_Source, C++_Source, C_Source,Java_Source, FORTRAN_Source, Verilog_Source, VHDL_Source,Assembly_Source, Pascal_Source, Cobol_Source, Ada_Source, Lisp_Source,Perl_Source, XQuery_Source, Hypertext Markup Language, Cascaded StyleSheets, JavaScript, DXF, Spice, Gerber, Mathematica, Matlab, AllegroPCB,ViewLogic, TangoPCAD, BSDL, C_Shell, K_Shell, Bash_Shell, Bourne_Shell,FTP, Telnet, MSExchange, POPS, RFC822, CVS, CMS, SQL, RTSP, MIME, PDF,PS (for source, markup, query, descriptive, and design code authored inthese high-level programming languages); C Shell, K Shell, Bash Shell(for shell program scripts); Plaintext (for otherwise unclassifiedtextual objects); Crypto (for objects that have been encrypted or thatcontain cryptographic elements); Englishtext, Frenchtext, Germantext,Spanishtext, Japanesetext, Chinesetext, Koreantext, Russiantext (anyhuman language text); Binary Unknown, ASCII Unknown, and Unknown (ascatchall categories).

The signature contained in the Signature and Tag Signature fields can beany digest or hash over the object, or some portion thereof. In oneembodiment, a well-known hash, such as MD5 or SHA1 can be used. In oneembodiment the signature is a digital cryptographic signature. In oneembodiment, a digital cryptographic signature is a hash signature thatis signed with the private key of the capture system 22. Only thecapture system 22 knows its own private key, thus, the integrity of thestored object can be verified by comparing a hash of the stored objectto the signature decrypted with the public key of the capture system 22,the private and public keys being a public key cryptosystem key pair.Thus, if a stored object is modified from when it was originallycaptured, the modification will cause the comparison to fail.

Similarly, the signature over the tag stored in the Tag Signature fieldcan also be a digital cryptographic signature. In such an embodiment,the integrity of the tag can also be verified. In one embodiment,verification of the object using the signature, and the tag using thetag signature is performed whenever an object is presented, e.g.,displayed to a user. In one embodiment, if the object or the tag isfound to have been compromised, an alarm is generated to alert the userthat the object displayed may not be identical to the object originallycaptured.

File System

In one embodiment, the capture system 22 implements an optimized filesystem to organize the object stored in the object store module 32 andthe content store 44 in particular. FIG. 7 illustrates a relationshipbetween the file system 700 and the storage complex 52. In oneembodiment, the storage complex 52 is made up in one or more disks thatmay be arranged redundantly according to RAID or some other storageprotocol. When the capture system 22 needs to access the content storeto store a captured object or to retrieve an object in response to aquery or the tag database, the capture system 22 accesses the storagecomplex 52 through a file system 700 that organizes the data on the diskand regulates read and write accesses.

Traditional all-purpose file systems are optimized for read operationsand efficient data editing. They accomplish this by using inodesorganized in a tree structure. In contrast, in one embodiment, filesystem 700 is optimized for write operations. Furthermore, since theobjects once captured should not be edited, efficient editing is not aconcern for file system 700.

In one embodiment, the file system 700 is a block-based file system.According to one convention, each block is 512 bytes, but other blocksizes can be used. The file system 700 further organizes the blocks intopartitions. In one embodiment, a group of contiguous blocks makes up apartition. Partitions can be the same size, but partition size may alsovary.

The file system 700 is now described in more detail with reference toFIG. 8. The file system includes an application program interface (API)for interfacing the file system 700 with the operating system,applications, and other components of the capture system 22. When anobject is to be stored, it is received through the API 802.

In one embodiment, the file system 700 implements a plurality of queues804-806 in which objects to be stored can be queued. In one embodiment,there is one queue associated with each object type. In otherembodiment, some object types that have no associated queue may beassigned to a catchall queue.

For example, queue 804 can be assigned to Emails, queue 805 can beassigned to Microsoft Word documents, queue 806 can be assigned to JPEGobjects, and so on. As discussed above, in one embodiment the contentstore 44 is partitioned by the file system 700. In one embodiment, eachpartition is associated with one of the queues (e.g. one of queues804-806) implemented by the file system 700. Thus, objects of a commontype are placed in one queue. When object from the queue are written todisk, each partition filled only has objects from the selected queue.

The file system 700 also includes a scheduler 808. The schedulercontrols the read and write bandwidth, and selects the appropriate queuefor writing. In one embodiment, the scheduler 808 implements a writepolicy that guarantees a certain write performance without regard forread performance. In other words, the scheduler 808 policy is such thatno read performance guarantee is made, so that a higher writeperformance can be guaranteed. In this manner, the scheduler 808optimizes the file system 700 for writes.

The scheduler policy can be adjustable based on user input. In oneembodiment, a user can select the level of write performance needed tobe guaranteed by the scheduler, up to the physical limit of the disk.The file system 700 also includes a block manager 810 that isresponsible for assembling objects into blocks to be written to disk andvice verse when reading from the disk. The file system 700 furtherincludes one or more disk controllers 812 that control the physicalreading and writing when interacting with the disk.

One embodiment of object read/write operations carried out by the filesystem 700 is now described with reference to FIG. 9. Blocks 902-906represent the arrival of objects from the capture device to the filesystem 700 that are to be written to disk. Since captured objects arestored on disk, there are generally more objects being written thanread. In block 902 a captured object is received from the other modulescapture system 22.

In block 904, the object type is determined. Since the object wasalready classified by content by the object classification module 30,determining the object type can be done by observing the content fieldof the tag associated with the received object, as discussed above. Inone embodiment, the possible object types mirror the possibilities ofthe content filed discussed above. In other embodiments, some contenttypes may be combined into object types, such as all word processingdocuments being combined into one object type rather than object typesspecific to each word processor. Similarly, various image protocols,such as JPEG and GIF, can be combined into an “Image” object type. Otherobject types not discussed as possible content filed values can also beimplemented. In yet another embodiment, the object type may be providedto the file system 700 making block 904 trivial.

In block 906, the received object is placed in a write queue accordingto object type. In one embodiment, there is one queue associated witheach object type. There may be catchall queues implemented, and not allqueues are necessarily the same size. The write queues have beendiscussed above with reference to FIG. 8.

In block 908, the file system scheduler 808 signals the beginning of thewrite process. In block 910, one of the queues is selected. As explainedabove, the selected queue will contain objects of one object typeassociated with the queue. As also explained above, in one embodiment,the disk is divided into partitions storing objects of like type. Thus,in block 912, a partition is selected such that the objects in thepartition are the same object type as the objects in the selected queue.If the partition selected is empty, then the selected partition becomesassociated with objects of the type contained in the selected queue.

In block 914, blocks representing the objects in the selected queue arewritten into the selected partition. In one embodiment, the blocks arewritten onto disk in a contiguous manner, one block after the other. Inthis embodiment, no complicated inode tree structure is used, since theobjects will not be altered after being written to disk. The writingprocess continues until the scheduler 808 switches to read processing inblock 916.

In one embodiment, for so long as write processing continues, theobjects from the selected queue are written to disk until the selectedqueue is empty, at which point another queue is selected. In anotherembodiment, objects from the selected queue are written to disk untilthe scheduler 808 selects a different queue. In one embodiment, if theselected queue becomes empty, the scheduler switches to read processing,if there are one or more read requests pending.

When processing a read request, starting at block 918, the diskcontroller 812 locates the first block of the object to be read on thedisk. In block 920, blocks are read into the file system 700 incontiguous blocks starting with the first block. Since there is no readpenalty associated with reading additional blocks, blocks are readcontiguously until another read request is processed.

Since object queries tend to request objects of like kind or temporalproximity, the arrangement of objects in partitions according to typemakes it more likely that objects requested in one query will be readwith no disk penalty (moving the disk read needle or waiting for diskrotation) following reading of the first requested object. In block 922,the blocks are reconstructed into the requested object or objects, whichare then provided to the capture system 22 in block 924.

General Matters

In several embodiments, the capture system 22 has been described aboveas a stand-alone device. However, the capture system of the presentinvention can be implemented on any appliance capable of capturing andanalyzing data from a network. For example, the capture system 22described above could be implemented on one or more of the servers 14 orclients 16 shown in FIG. 1. The capture system 22 can interface with thenetwork 10 in any number of ways, including wirelessly.

In one embodiment, the capture system 22 is an appliance constructedusing commonly available computing equipment and storage systems capableof supporting the software requirements. In one embodiment, illustratedby FIG. 6, the hardware consists of a capture entity 46, a processingcomplex 48 made up of one or more processors, a memory complex 50 madeup of one or more memory elements such as RAM and ROM, and storagecomplex 52, such as a set of one or more hard drives or other digital oranalog storage means. In another embodiment, the storage complex 52 isexternal to the capture system 22, as explained above. In oneembodiment, the memory complex stored software consisting of anoperating system for the capture system device 22, a capture program,and classification program, a database, a filestore, an analysis engineand a graphical user interface.

Thus, a capture system and a file system for the capture system havebeen described. In the forgoing description, various specific valueswere given names, such as “objects,” and various specific modules, suchas the “queues” and “scheduler” have been described. However, thesenames are merely to describe and illustrate various aspects of thepresent invention, and in no way limit the scope of the presentinvention. Furthermore various modules can be implemented as software orhardware modules, or without dividing their functionalities into modulesat all. The present invention is not limited to any modular architectureeither in software or in hardware, whether described above or not.

The invention claimed is:
 1. A capture system, comprising: a file systemconfigured to organize data on a disk and to regulate read and writeaccesses; a plurality of queues associated with captured objects thatare received through the capture system via network traffic, wherein thequeues are associated with captured objects based on content of thecaptured objects, and wherein the disk is divided into a plurality ofpartitions for storing at least some of the captured objects, whereinthe captured objects are indexed with a tag database comprising a datastructure, in which each record of the data structure is configured toindex a corresponding captured object according to information about thecaptured object, the information of each captured object including acontent type associated with the captured object; a scheduler configuredto select one of the plurality of queues for performing a particularwrite operation, wherein the scheduler implements a write policy thatdefines a threshold level of write performance to optimize the filesystem for write operations over read operations, and wherein thethreshold level of write performance is adjustable up to a physicallimit of the disk; and a block manager configured to select one of thepartitions of the disk, wherein blocks of data are written from theselected queue to the selected partition.
 2. The capture system of claim1, wherein the file system is a block-based file system includingcontiguous blocks that form the plurality of partitions.
 3. The capturesystem of claim 1, wherein the file system includes an applicationprogram interface (API) for interfacing with an operating system of thecapture system.
 4. The capture system of claim 1, further comprising: acatchall queue for objects not having their own designated queue basedon content.
 5. The capture system of claim 1, wherein each one of theplurality of queues is associated with the captured objects based on anobject type of the captured objects, and wherein object typedeterminations are performed by identifying a content field of a recordassociated with a particular captured object.
 6. The capture system ofclaim 1, wherein at least one of the queues is associated with e-mailsor word processing documents.
 7. The capture system of claim 1, whereinthe captured objects represented by particular blocks of data can beretrieved in response to a query to search for a tag included in one ormore of the captured objects.
 8. The capture system of claim 1, whereineach one of the plurality of queues is associated with the capturedobjects based on a content type of the captured objects, and wherein acontent field of a record associated with a particular captured objectrepresents the content type of the particular captured object.
 9. Amethod, comprising: receiving network traffic via a capture systemconfigured for capturing objects, wherein the capture system includes afile system configured to organize data on a disk and to regulate readand write accesses, wherein the capture system further includes aplurality of queues associated with captured objects that are receivedthrough the capture system via network traffic, wherein the queues areassociated with captured objects based on content of the capturedobjects, and wherein the disk is divided into a plurality of partitionsfor storing at least some of the captured objects, wherein the capturesystem further includes a scheduler configured to implement a writepolicy that defines a threshold level of write performance to optimizethe file system for write operations over read operations, and whereinthe threshold level of write performance is adjustable up to a physicallimit of the disk, and wherein the captured objects are indexed with atag database comprising a data structure, in which each record of thedata structure is configured to index a corresponding captured objectaccording to information about the captured object, the information ofeach captured object including a content type associated with thecaptured object; selecting one of the plurality of queues for performinga particular write operation; and selecting one of the partitions of thedisk, wherein blocks of data are written from the selected queue to theselected partition.
 10. The method of claim 9, wherein the file systemis a block-based file system including contiguous blocks that form theplurality of partitions.
 11. The method of claim 9, wherein the filesystem includes an application program interface (API) for interfacingwith an operating system of the capture system.
 12. The method of claim9, further comprising: a catchall queue for objects not having their owndesignated queue based on content.
 13. The method of claim 9, whereineach one of the plurality of queues is associated with the capturedobjects based on an object type of the captured objects, and whereinobject type determinations are performed by identifying a content fieldof a record associated with a particular captured object.
 14. The methodof claim 9, wherein at least one of the queues is associated withe-mails or word processing documents.
 15. The method of claim 9, whereinthe captured objects represented by particular blocks of data can beretrieved in response to a query to search for a tag included in one ormore of the captured objects.
 16. The method of claim 9, wherein eachone of the plurality of queues is associated with the captured objectsbased on a content type of the captured objects, and wherein a contentfield of a record associated with a particular captured objectrepresents the content type of the particular captured object.
 17. Logicencoded in non-transitory media that includes code for execution andwhen executed by a processor operable to perform operations comprising:receiving network traffic via a capture system configured for capturingobjects, wherein the capture system includes a file system configured toorganize data on a disk and to regulate read and write accesses, whereinthe capture system further includes a plurality of queues associatedwith captured objects that are received through the capture system vianetwork traffic, wherein the queues are associated with captured objectsbased on content of the captured objects, and wherein the disk isdivided into a plurality of partitions for storing at least some of thecaptured objects, wherein the capture system further includes ascheduler configured to implement a write policy that defines athreshold level of write performance to optimize the file system forwrite operations over read operations, and wherein the threshold levelof write performance is adjustable up to a physical limit, of the disk,and wherein the captured objects are indexed with a tag databasecomprising a data structure, in which each record of the data structureis configured to index a corresponding captured object according toinformation about the captured object, the information of each capturedobject including a content type associated with the captured object;selecting one of the plurality of queues for performing a particularwrite operation, and selecting one of the partitions of the disk,wherein blocks of data are written from the selected queue to theselected partition.
 18. The logic of claim 17, wherein the file systemis a block-based file system including contiguous blocks that form theplurality of partitions, and wherein the file system includes anapplication program interface (API) for interfacing with an operatingsystem of the capture system.
 19. The logic of claim 17, wherein theplurality of queues includes a catchall queue for objects not havingtheir own designated queue, and wherein the captured objects representedby particular blocks of data can be retrieved in response to a query tosearch for a tag included in one or more of the captured objects. 20.The logic of claim 17, wherein each one of the plurality of queues isassociated with the captured objects based on an object type of thecaptured objects, and wherein object type determinations are performedby observing a content field of a record associated with a particularcaptured object.